The tolerance and toxicity of clarithromycin.

In a programme of Phase II and III trials, 3437 patients received clarithromycin. Twenty percent of these patients reported adverse events, and three-quarters of these were thought to be possibly or probably linked with the drug. Only 1% of these were severe and most of the adverse events (11% of patients) were digestive system upsets. There was no significant relationship between the dosage of clarithromycin and the incidence of adverse events. Comparison between clarithromycin and the other antibiotics used in controlled trials showed similar side effects reported for beta-lactam agents and clarithromycin but adverse events were reported less frequently with clarithromycin (19%) than with erythromycin (29%) and other macrolides. This was particularly noticeable for adverse events of the digestive system (9% with clarithromycin vs 20% with erythromycin). No significant haematological, hepatic or renal toxicity due to clarithromycin was reported. There may be slight elevation of theophylline levels during concomitant clarithromycin administration.